Typical microelectronic systems have various electronic components that often share one or more common biasing circuits. Examples of circuits that have common biasing arrangements include current sources, operational amplifiers, comparators, as well as other various analog functions.
Most biasing circuits that utilize metal oxide semiconductor (MOS) type transistors which have two stable operating states, one state where the MOS transistor is on or active, and another state where the MOS transistor is off or inactive. Since biasing circuits do not provide any utility when the transistors are off, a start-up circuit is often used to ensure that the biasing circuit reaches an active operating state after power is applied. Many biasing circuits have the desirable property that after they complete the task of ensuring active operation they cease to influence the operation of the biasing circuit with as little current consumption as possible.